Part 1. I know the name or number of the discontinued chart I want.
(a) Go to Part 3.
Part 2. I do not know what charts were available that no longer exist.
(a) First we need to find out what charts existed. There is a list of all charts at NOAA but we cannot tell from that what they covered, so we use a trick to learn the names of charts and what they covered. Download this file Historic_NOAA_charts.kml that we will then load into Google Earth (GE), which will show all the historic chart outlines.
Above is what you see after dragging the KML file onto GE, or maybe just double clicking the file might open GE and load the KML file. Then you can zoom into see the charts.
(b) Mouse over a chart outline to highlight it then left click to get the info. This is an example of a discontinued chart, 18433 Haro Strait Middle Bank to Stuart Island. We once had a full set of these spanning the San Juan Islands at 1:25,000 but they are all gone. For now there is just one 1:80,000 for the whole region—but we should get new reschemed 1:22,000 set of ENC sometime early next year.
(Note that if the chart still exists, you can click one of the preview options and see it, but it is easier by other methods to do that....see starpath.com/getcharts.)
For this example, we assume this is the only one we want, ie we want a copy of the Last Edition of this chart, which was discontinued about two years ago—so the one we get is going to be out dated.
(c) Now that we know the chart we want, we can go to Part 3.
Part 3. Get a copy of a chart whose name or number I know
(b) On the first page, click the link to Hide the map search.
(c) Then enter the chart number... space is too small but it will take it! Then press Search.
(d) Now we see the chart we want, Last Edition of 18433. We can download a JPG of PDF of the image. These PDFs are not georeferenced, like the NCC PDFs are. So if we want to load this chart into a nav program, we might as well use the JPG, which we can manually georeference in several nav programs.
We can also take a look at the chart with the Preview link. Again, we are looking at an historic item. We could have several reasons to want this, but we must remember it is outdated.
Same image zoomed in to show it is a high-res image.
Part 4. How to load a historic chart (georeferenced) into a navigation program
(a) To be added. It takes just a few steps and a minute or two!
Traditional paper charts will all be gone in six months; most are gone now. Here is a summary of the USCG's official chart carriage policy, followed by a short background, some details, and direct links to the references.
(1) A non-ECDIS vessel that is required to carry nautical charts may meet that requirement with NOAA Custom Charts (NCC), providing they are up to date (within 6 months) and made at adequate size and scale needed for safe navigation in the waters covered, and preferably on adequate paper quality for routine navigation plotting underway.
(2) A non-ECDIS vessel on inland waters that is required to carry nautical charts may meet that requirement in lieu of any paper charts on board with an ECS of their choice, providing they are viewing official NOAA ENC, using an adequate size screen for safe navigation (large tablet or computer), and the ENC are up to date.
(3) Vessels in coastal waters, when relying on electronic charting alone, must display official ENC on an ECS that meets more stringent environmental standards that are outlined in NVIC_01-16 (ch 2)—and under further development at the moment. The ECS manufacturer must provide a declaration of conformity. In the meantime, appropriate NCC can be used in coastal waters.
Sample section of a NOAA custom chart (NCC)
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Five years ago, NOAA announced to the world that they had begun the process of discontinuing all traditional paper charts and related chart products such as raster navigational charts (RNC), PDF charts, etc. They said it will be a gradual process, but all traditional paper charts will be gone by the end of 2024.
And they have kept their word on this; at the moment, five months from the promised completion date at the end of this year, we have only 195 charts left of the 1100 or so that existed five years ago, and all of those left are marked last edition (LE). They have not been updated for months, and will not ever be. Even these last charts are already historic items. (The last edition of each NOAA chart once discontinued is available at historicalcharts.noaa.gov.)
Traditional paper charts, with their fixed sizes, scales, and coverage areas, are being replaced with new versions of electronic navigational charts (ENC), downloaded at no charge from NOAA. They are updated daily at 0500 UTC. If we want to know what is changed on the LE charts left, we need to check the corresponding ENC.
NOAA is also offering now a new form of printed chart called a NOAA custom chart (NCC) that is based upon the latest ENC data. These NCC play a key role in our chart navigation going forward, as discussed below.
In short, this historic and impactful revolution in charting is indeed taking place. Several major maritime nations have similar plans for ENC to play a larger role in their chart production, but the US will lead the way, as it has historically with other aspects of electronic charting. The UKHO, for example, had announced a similar deadline for their transition to all ENC, but has since postponed the date, perhaps in part because they had not worked out the carriage requirements that is the topic at hand for US vessels.
ENC are not a new concept, even though the new reschemed versions are significant improvements over the legacy versions. ENC have been in use since the mid 1990s. Since 2018, ENC have been required on nearly all commercial vessels on international voyages. These international ships, and other classes of ships in US waters are required to display the ENC using a type-approved hardware and software system called ECDIS (electronic chart display and information system). But these classes of large "ECDIS vessels" are not a subject at hand, because their rules on charts are not affected by the demise of traditional paper charts.
The International Hydrographic Organization (IHO) specifies the standards for the content and format of ENC in a document called IHO S-57. The IHO also specifies how ENC should appear on the navigator’s chart screen in IHO S-52. An ENC of any nation by definition meets the requirements of S-57, and ECDIS chart display from any manufacturer by definition meets the requirements of S-52.
In Jan, 2016, the USCG announced (NVIC_01-16) that all commercial vessels not required to use ECDIS, may use ENC in lieu of paper charts, and spelled out the details required. Chart display systems (nav apps and chart plotters) that do not meet ECDIS standards are called electronic charting systems (ECS)—which is not a generic name, it is an official IHO definition.
This document was then notably updated in May, 2020 (NVIC_01-16_ch2) and added clarification of the use of electronic versions of other required publications such as the Navigation Rules Handbook, Coast Pilots, Light Lists, and tide and current data—recall that in 2020 NOAA discontinued the authorized publication of annual tide and current tables that use secondary station corrections (Tables 2), and since then it is up to mariners to create their own appropriate tables for required stations using the convenient options at tidesandcurrents.noaa.gov. Tables 2 corrections still in print today are not authorized nor dependable.
Then in June, 2023 an historic internal USCG Policy Letter (NAVPOLTR_01-23) explained the crucial role of NCC.
Those two documents spell out the rules on chart carriage and display that govern chart carriage after the end of this year when all traditional paper charts will be gone—and they govern the policy right now for areas where there are no paper charts left of an appropriate scale for safe navigation.
Please read the full documents linked below. My notes here are only brief paraphrases.
Chart Carriage Requirements During NOAA Chart Sunsetting Plan,
• Though not stated elsewhere to my knowledge, this document confirms that NOAA custom charts NCC will be accepted as meeting chart carriage requirements, provided:
(1) They are up to date (within 6 months)
(2) Made at an adequate scale and paper size for safe navigation in the waters at hand
(3) Preferably printed on adequate paper quality for routine navigation plotting underway
• The preference (3) suggests using one of the existing print on demand (POD) chart printers. Several are set up to accept a mariners homemade NCC, and some are offering predesigned NCC options that replicate as near as possible the traditional chart coverages. They are accustomed to chart printing on quality paper.
• The Policy Letter does not rule out individual printing of chart booklets on smaller size paper similar to those used in commercial chart booklets. The economic 34" x 22" option (ANSI D) might meet single chart or booklet applications for smaller commercial vessels.
• The Policy Letter anticipated an important advance in the NCC program that has since been implemented. Namely, in NCC ver 2.0, mariners can save their NCC designs and then return to them and with two button clicks create an updated version of their saved NCC design. We anticipate NCC app ver 3 in mid July.
• Also noted in the Policy Letter is the fact that NCC do not have chart numbers so there are no Local Notices to Mariners presenting proposed or actual changes for specific NCC, but mariners can check on line for latest ENC updates to the regions they have charted and that way decide if a new NCC is needed or not from their saved NCC design—this is a new update to this updates page, making it even easier stay aware of ENC updates that could affect the NCC.
• It should be noted that the Policy Letter has an expiration date of April, 2025. So until something shows up in the CFRs we should be be aware that things could change at that time.
• References: CG-NAV Policy Letter 01-23, 8b (1) and (2)
Use of Electronic Charts and Publications in Lieu of Paper Charts,
Maps and Publications,
Navigation and Vessel Inspection Circular number 01-16, 16700.4
Again, please read the full document; it includes an interesting history of paper and electronic charting. My notes are just brief paraphrases, with these short takeaways...
• The rules for electronic charts only (no paper charts on board) are different for inland vs coastal waters, where "coastal waters" in this context means anywhere on the outer coast, seaward of the MLW line.
• On inland and coastal waters, however, the key factor is we must use official NOAA ENC that are up to date and of adequate scale for the navigation at hand. (This is not a major concern, because most suitable ECS (nav apps), and there are many as noted in the NVIC, offer the option to check for latest updates and load all scales available with a couple button clicks.)
• We stress that third-party charts or charts described as "based on ENC", "modified ENC," "Enhanced ENC," etc, do not qualify. For non-ECDIS vessels to rely on electronic charts only, they must use official NOAA ENC, presumably obtained directly from NOAA, who provides them at no charge, updated daily at 0500 UTC when changes are confirmed. Light List changes take about a week or so to enter into the affected ENC updates.
• A non-ECDIS vessel on inland waters that is required to carry nautical charts may meet that requirement in lieu of any paper charts on board with an ECS of their choice, providing they are viewing up to date NOAA ENC, using an adequate size screen for safe navigation. This is not spelled out more specifically here, but we can note that the IMO Performance Standards for ECDIS, Sec 10.2, calls for a minimum screen size of 270 mm x 270 mm (10.6" x 10.6"), which is about the size of a nominal 13" laptop or an iPad Pro—keeping in mind that ECDIS standards are not required for inland ECS usage.
• Non-ECDIS vessels traveling in coastal waters when relying on electronic charting alone, must display official ENC on an ECS that meets more stringent environmental standards that are outlined in NVIC_01-16 (ch 2)—and under further development at the moment. The ECS manufacturer must provide a declaration of conformity. In the meantime, appropriate NCC can be used in coastal waters.
• This NVIC also clarifies that digital copies (PDFs, for example) of tide and current data, Coast Pilots, Light Lists, and Navigation Rules Handbook can also meet similar carriage requirements—which is a reminder to all vessels, even those not formally required to carry such documents, that they can meet prudent safe-navigation document needs with digital products.
The active government agencies, USCG, NGA, and several divisions of NOAA, make it very easy to download the documents and keep them up to date. Storing them in the library of your favorite ebook reader is one way to organize them, with convenient search, bookmark, and highlight tools. Ship and instrument manuals can be in another library folder.
Sample ENC section of the same region shown above as NCC, viewed in qtVlm. This ENC has a compilation scale of 1:12,000. It can be zoomed to show detail.
Zoomed section of the above. Many ECS offer the option to highlight sector light coverage; in this case we see the green light marking the top of the main San Diego Bay entrance range
Summary
These basic rules for the smaller commercial vessels that do not require ECDIS seem very reasonable and practicable. The ECS "of our choice" to view the ENC could be any of the many commercial and even free versions available now, such as Coastal Explorer, TimeZero, Expedition, OpenCPN and qtVlm. All show official ENC with convenient means of chart downloading and semi-automatic chart updating. They run on computers and some on large tablets, and all include the range of functionality wanted in a versatile ECS. There are certainly numerous others we have not tested.
The NCC program for the paper chart alternative is very attractive and slowly becoming better known. There is certainly room to improve, especially with regard to terrain coverage, but this is understood and on the table to be improved. Indeed, with all the GIS information available these days on elevation contours, roads, building, ground cover, and so on, we can expect NCC of the future to be superior in this regard to the limited but valuable examples on the paper charts being discontinued.
Recreational mariners are not directly affected by chart carriage requirements of commercial vessels, but it is fair that they look up to their rules as guidelines to prudent navigation. And all mariners are, of course, bound by Rule 2a ("good seamanship rule") of the Navigation Rules.
Sailing and Navigation Schools
On the water training of students who paid for the training are required to have a USCG licensed instructor and the vessels are required to have authorized nautical charts on board. Between now and the end of the year, if there is still a traditional NOAA chart available of adequate scale for safe navigation then a copy of that chart will meet this need until Jan 1, 2025. After that, the training vessel must have either an NCC made as noted above, or have a tablet or computer showing official NOAA ENC of the area as explained above. Third party charts do not meet the requirement, and viewing on a small screen (ie phone) alone will not meet the need according to the documents presented.
On the water training in certain restricted waters that do not require a licensed operator do not have these chart requirements, but simple prudence would call for them in any event. As noted, Rule 2a still applies to all navigable waters, as do perhaps local and state rules.
It seems logical that all navigation training should begin the transition to NCC in place of the historic training charts, which have frankly been distractingly outdated for many years. We are now working on NCC replacements for 1210tr and 18465tr. The challenge is creating NCC that have adequate labels so the many standard exercise books and tests in use nationwide for decades can be adapted to the new NCC. We also have a unique challenge of how to cover a significant section of 18465tr that is now only covered by a Canadian ENC.
Even though the historic training charts will remain available, it seems a disservice to students to continue to use them. NOAA has helped with this transition in that they use on the NCC the traditional chart symbols for all ATONS, rather than the official ENC symbols. Presumably that will change in a year or two... or at least we will have the option to show old symbols or official ENC symbols.
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Our text and reference books on ENC usage can be seen at starpath.com/ENC
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I will be adding a series of videos on the background for this post, starting with this one:
Strong winds come from a variety of weather patterns. Some are large like a mid-latitude Low, some mid-size like a tropical wave, and some quite small like those found in narrow gaps between islands. Some winds are transient like a downdraft from a passing thunderstorm while others are more persistent like the strong summer winds along the southern Oregon and northern California coast.
Strong winds from larger, longer lasting weather systems are generally well quantified by weather models and included in the official forecasts. But smaller scale, shorter duration winds can fall below the resolution, temporal and spatial, of weather models and can be better described by how likely they are to occur in generalized areas. Winds driven by Wake Lows fall into this latter category.
A Wake Low is defined by the American Meteorological Organization as:
a surface low pressure area or mesolow (or the envelope of several low pressure areas) to the rear of a squall line; most commonly found in squall lines with trailing stratiform precipitation regions, in which case the axis of the low is positioned near the back edge of the stratiform rain area.
Because squall lines are bands of thunderstorm, (a.k.a squalls when over water) typically ahead of cold fronts, it is useful to look at the structure of a single squall.
The squall has a life cycle that starts with a growing phase. In this initial phase, surface winds flow radially inward at the base. These we watch with a weather eye to see if they may eventually become towering cumulonimbus. If they grow to full maturity, there is a second phase that has a downdraft creating strong wind that comes with heavy rain, perhaps even hail.
Wind patterns with the two phases of the squall are shown in Figure 1. Notice the strong winds from the downdraft are in front of the squall while behind it the wind can be light or flukey. The difference in the winds fore and aft of the squall is because the speed of the movement of the squall adds to or subtracts from the wind circulating in the squall.
Figure 1 (from Modern Marine Weather by David Burch)
In Figure 2, typically the squall movement would be from left to right. In the mid-latitudes that would be roughly west to east or in the trade winds from east to west. Because squalls are embedded in and move with the upper level winds, it is best to review the 500 mb maps or model data or even local soundings to get a sense of squall movement.
Figure 2
Figure 3 shows the atmospheric pressure distribution along the cross-section shown in Figure 2. The Mesohigh is found under the core area of Figure 2 and the Wake Low is in the area under the stratiform clouds.
Figure 3
As the squall moves from left to right, the leading low pressure area experiences strong winds blowing from the Mesohigh and toward the low. This is the source of the common wind gusts commonly experienced on the leading edge of a squall.
On the aft side of the squall, the wind is again driven by the Mesohigh toward low pressure. Because this area of low pressure is on the aft side of the low or in its “wake”, the term Wake Low seems to fit. One key takeaway is that the wind direction will reverse or at least make a very large veer due to the reversal of the pressure gradient as the squall passes. How quickly the wind direction changes would be affected by the strength of the pressure gradient and speed of the squall.
Wind speeds can be estimated using the pressure gradients and scaling provided in Figure 3. With some unit conversions, the pressure gradient in millibars/degrees latitude would be about 4 mb/0.6*. From Figure 4, assuming 45* latitude, this gradient estimates a wind speed of 76 kt! Although this is just a graphic for demonstration purposes, the magnitude of the wind speed is worth noting.
Figure 4
Figure 5 is from a case study of a Wake Low that occurred on September 2, 2010. The National Weather Service analyzed the pressure drop over a 2 hour period (blue dashed contours) of up to -3 mb. The Duluth International Airport actually observed a 6.1 mb pressure drop in only 28 minutes resulting in a wind speed of 50 kt.
Figure 5
Because Wake Lows are a relatively small scale, short duration event, they are difficult to forecast in terms of wind direction and speed at a specific time and location. However, squall or thunderstorm potential is routinely forecast by the NOAA Storm Prediction Center in its Mesoscale Discussions and Convective Outlooks for CONUS and coastal waters, Figure 6.
Figure 6
While the case studies tend to be in the upper mid-west area of CONUS, they do not suggest that Wake Lows would be limited to those areas. It may just be that only over land is there enough observational data to support the analysis of this relatively small-scale, transient event. This leaves mariners to ask whether winds resulting from Wake Lows could happen more generally anywhere squalls are found. After all, strong winds that radically change direction are something to look out for!
Summary
·Wake Lows are atmospheric low pressure areas found on the aft side of squall lines
·Fluctuating pressure gradients caused by Wake Lows can cause dramatic changes in wind direction
·Strong winds are a potential both on the leading and trailing sides of squall lines
·Wake Lows are small scale, transient events that may be anticipated where squall lines are forecast
·For safety, anticipate strong and gusty winds, as well as heavy rain and lightning with cumulonimbus clouds
We are one of the first in line to lament the poor coverage of terrestrial charting in electronic navigational charts (ENC) compared to the paper chart coverage we are used to. And for good reason: we do most piloting relative to landmarks and much of the land mass on ENC is conspicuously blank—which can appear even more moonscape vacant depending how we have the display set up, as shown below.
Unlike viewing raster navigational charts (electronic copies of the paper charts), ENC let the user control many aspects of the display. Above we see an example of choosing to show "Important text only," which is a (misleading) official ENC display option.
If we compare that to what we see on the equivalent paper chart, we see what we are missing in that view.
It is not just the names that can be hidden, but NOAA ENC have very few elevation contours which can often help with piloting.
Another reason we care about charted place names is a matter of basic safety and prudent seamanship. We teach that it is good policy to always keep in mind a verbal description of where you are, and maybe even note it in the log book that way, ie "Just passing west of Willow Island." Knowing this at all times we are prepared to describe our position over the radio in an emergency—which is much faster than finding, if you can, a read out of the Lat and Lon and reading that with its potential error. Furthermore it makes the cruise more enduring if you learn these names as you go by. The say-it-out-loud method is is also how we teach students to learn the stars in cel nav.
Thus these charted place names are valuable to navigation. But things are not so bad as they might appear. They can be bad, as shown above, but they do not have to be. Below we turn on the text labels to see what we really do have in ENC.
The charted place names are actually all there on the ENC, they are just not as prominent as they are in the paper charts, which have the freedom to use large font sizes for some, and indeed print on a curve.
ENC have strict international rules of font size and orientation, although in some cases they do let labels (and associated symbols) move on the chart so that critical ones remain in view as you change the screen. A folded paper chart on the chart table may be just hiding a note that a dashed line is marking a restricted Navy firing zone. On the equivalent ENC if you panned that notice off the screen it would suddenly reappear in a new position in view.
In other words, the use of labels on an ENC is just one more aspect of the new chart reading skills we need to develop for ENC. We have to look at the charts in a new way. One thing that helps with this is the rule that ENC chart symbols and labels stay the same size regardless of the display scale (zoom level). Thus crucial matters may become more apparent as we zoom into the region of interest.
The Future of ENC
As for other deficits of the terrestrial coverage of existing NOAA ENC, we can be confident that this will improve. First of all, a few nations do a better job with the elevation contours already, and the US certainly has extensive GIS data for all aspects of US mapping.
To show that big agencies like NOAA should be able to solve this problem fairly soon, we can show how to do this ourselves already. Beyond its outstanding ENC display presentation, the popular navigation and weather app qtVlm also offers the option to overlay on the chart GIS data as shape files (.shp), a standard format for GIS data.
In the sample below, I followed the instructions we have online to add the roads to Lopez Island and water bodies and elevation contours to Blakely Island, and then (within qtVlm) limit the contours to the 100 ft intervals shown on the paper chart.
Once these are installed, we can get a tool tip presentation of the road names, heights of elevation contours, and related data for water bodies. In fact we learn there are more lakes on Blakely Island than the paper chart showed.
In other words, there is good reason to expect that the terrestrial coverage of future ENC will be even more valuable than that of the paper charts they are replacing.
We are likely to see this take place first in the printed versions of the ENC called
NOAA Custom Chart (NCC). These are intended to be the (non-official) paper backups of the official ENC viewed on a computer screen or chart plotter [See new note below]. NCC are user-created online from the NOAA NCC app that produces a PDF chart of the desired region, scale, and paper size, based on the ENC content for that region. Then it is up to the user to get the chart printed at the chosen paper size.
It is during this NCC production that NOAA could offer the GIS overlay options such as elevation contours, roads, building, water bodies, etc to be added to the PDF they are creating... essentially just as qtVlm offers users the option as shown above. Thus we could end up with a new-generation of paper charts that are indeed superior to what we are now accustomed to.
Seeing this new data in the actual ENC themselves is likely further down the line. Even though a few other nations already have better contours, roads, and buildings, NOAA is likely pretty tied up with their massive process of rescheming all the ENC, which is a major ongoing improvement to the watery parts of the ENC. Not to mention that all nations are in the long process of preparing for the next generation of ENC, where the present IHO S-57 standard will be replaced by the new S-100 standard, which inherently includes a lot of new GIS content. These proposed changes are discussed in our text Introduction to Electronic Chart Navigation.
This week is the 30th anniversary of the opening of the EuroTunnel (Chunnel) between England and France. The BBC commemorated the event with a story about the first underground meeting of the tunnels being dug from both sides that took place on Dec 1, 1990, four years before the actual opening of tunnel to traffic in 1994. They met roughly mid channel, with TV cameras at hand.
The fellow on the British side with orange t-shirt is Graham Fagg who in 2010 gave a description of the event, which can be heard on the BBC Witness program. In that recording from (3:59) to (4:28) we learn that when the hole was opened up big enough to walk through there came a sudden wind from the British side to the French side that was strong enough to blow his helmet off. That wind is the subject at hand.
This wind is quite literally what we call in marine weather a channeled wind! It means the pressure on the UK side was higher than that on the French side and the area between the two sides was confined by a narrow channel. We just have a case here of a very narrow channel, not just steep hills on two sides.
Our goal is to estimate what that wind speed was, which is an exercise in resources—meaning, can we find the actual pressures at both ends at that time, and then can we make some semi-reasonable estimates of the wind speed.
Below shows the Chunnel viewed on Meltemus charts of UK in qtVlm, with overlaid ECMWF reanalyzed surface analysis for the approximated break-though time (11 to 12 UTC, Dec 1, 1990) when the wind was noted. (The New York Times had a good article about the event, but gave the wrong time of day due to a time zone error! — no link here as they no longer let non subscribers read their articles.)
The red line is the route of the Chunnel. The isobars are shown at 0.1mb spacing. The inserts are meteogram plots of how the pressure varied throughout the day at both ends. The pressure gradient across the channel did not change from 11z to 12z, at (1036.0 - 1035.5)/26.9 = 0.5mb/26.9 nmi.
The ambient surface wind at this time was about 10 kts across the channel, but we must use wild approximations to estimate the wind in the tunnel.
We can for example just use the basic formula for wind responding to isobars that leads to the wind we see on the surface. We derive a simple formula for that in Table 2.4-1 of Modern Marine Weather:
U = 40 kts/ [D x sin(Lat)]
Where D is the pressure gradient expressed in a special way. Namely it is the distance between 4-mb isobars expressed in degrees of Lat. On a map, we put dividers across adjacent isobars, then move that to the Lat scale. If the distance between the two isobars on either side of the point we care about is 180 nmi, then D = 3.0.
So we have to convert our tunnel gradient to that format starting with: 0.5 mb = 26.9 nmi.
0.5 mb x (4/0.5) = 4 mb = 26.9 nmi x (4/0.5) = 215.2 nmi = 3.58 Lat degrees (at 60 nmi per degree).
U = 40 kts / [3.58 x sin (51)] = 14.4 kts
Then for surface winds we have a surface friction reduction of 0.8 or so that leaves us with 11.5 kts, which essentially agrees with the observed surface winds—which should not be a surprise as that is the basic procedure used by the models, with a few subtle corrections.
The above is based on the physics of wind flow, but still a large stretch to project that thinking into the tunnel. It is at least a plausibility argument for the rough magnitude of the wind.
In our textbook in Sec 6.2 on Wind Crossing Isobars (page 146) we give another way to approximate wind flow in channels that is purely empirical, meaning not computed, just observed. It is a rule we compiled based on how the local NWS forecasted wind speed (in the old days) in the Strait of Juan de Fuca and in the Puget Sound based on the pressure differences at each end of these channels. Our composite guideline is this:
Channel wind (kts) = 800 x Pressure gradient (mb/nmi),
which we can easily apply to what we know:
Channel wind = 800 x (0.5/26.9) = 14.9 kts.
So again, we see the order of magnitude of the wind speed we might expect in the tunnel. And again, we cannot consider this rigorous science; wind flow in restrictions is very complex. We have just confirmed that indeed the wind was going the direction observed, and also about the right speed. We use this same approach to forecast or anticipate wind changes in our own waters based on pressure changes. It is part of our Local Weather web page.
There is also a physiological element of confirmation. The force of the wind is proportional to the wind speed squared. The force of 14 kts of wind is twice that of 10 kts of wind. At 17 kts it is three times stronger than 10 kts. In other words, there is a dramatic difference in what we experience in 10 kts vs even just 12 kts.
We know from our own experience that we could be in a wind of 10 or 11 kts that could blow our hat off if it hit at the right angle. And it would be noted, but not a focus point for any newscaster's story. But if this wind were much more, we know that it would be a focus of the conversation, which it wasn't. Note too that the wind came not at the moment when the flags were exchanged, but later when they had the hole opened up enough to walk through.
In other words, without any math or science considerations, we might guess the wind was about 8 to 10 kts, because less than that would not blow his helmet off, and much more than that would have clothes rippling in the wind and newscasters talking about it, which they did not.
Such visual effects of the wind is not unlike our view of whitecaps. At 10 kts there are some, if we look carefully; at 15 kts they are easier to see; but at 20 kts they are the dominant factor noted when looking at the water.
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Pressure remains a concern in all such tunnel travel due to the piston effect that can create high pressures in front of the train stressing gear and making travelers uncomfortable. The Chunnel has build in pressure escape valves all along the tunnel to prevent this.
Chunnel prices seem to be like Amtrak, which depends on availably, and season.
We had an excellent question come up in class asking simply what are the best weather resources for the waters of Japan? In our textbook (Modern Marine Weather) and in our training and resources app (Weather Trainer Live) we list all resources available worldwide and even have sections on specific regions, but realize it could be valuable to just focus in and list specific solutions for a sample area, with details needed to actually obtain the data underway.
So we use Japan for this example, stressing that these same sources (or counterparts) are available for essentially any part of the world.
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(1) Model forecasts in grib format The main workhorses we use anywhere will be the global model forecasts from GFS and ECMWF. These data are available from saildocs with an email request to query@saildocs.com with this in the body of the message:
These files can then be viewed in any navigation app, such as qtVlm, OpenCPN, TimeZero, Coastal Explorer, or Expedition or in a dedicated grib viewer such as XyGrib. Background on use of gribs at the Grib School. Luckgrib is a state of the art app for downloading and viewing grib data.
Sample model forecasts. Red is GFS, blue is ECMWF
(2) Graphic weather maps We need to check the pure model data from above with actual maps made by human meteorologists, and we have several sources of those.
Above is a sample surface analysis (12z Apr 28) and below is the corresponding OPC map, which is as far west as they go (135E).
These are pdfs of about 550 kb, too large for sat phones as a rule, but it won't be long till all mariners have high speed internet offshore, then this type of link becomes more valuable. In the meantime, a supporter on land can download the file, copy the image from the pdf, reduce the file size, and email it to you on the boat.
Graphic weather maps are also available by HF radiofax if your boat happens to have the SSB radio and antenna set up. Japan stations are listed in the Worldwide Marine Radiofacsimilie Broadcast Schedules. The many JMA maps available this way are listed at the JMH radio Station.
The other important radio related resource for international voyages is the NGA Pub 117, Radio Navigational Aids. This tells, for example, what time of day you get VHF storm and navigation warnings for different parts of Japan. NAVTEX broadcast times are also given.
HF Fax is frankly an outdated technology (replaced by satellite communications), but if we could access the folder JMA store the images in we could request the same maps by email the way we do the US maps.
(2b) US OPC maps covers NW Japan waters
US maps only go to 135E (sample above), but they could be helpful on the approach from the east. See the Starpath Pacific Briefings page for examples and links. These are easy to obtain by email from Saildocs or FTPmail.
(2c) You can see UK maps of Japan waters at
https://charts.ecmwf.int/ and choose Eastern Asia region. These maps, however, might be just their model output plotted, which does not add knowledge.
(3) Satellite cloud pics Japan has an excellent satellite image program (Himawari). See index to files here, which is also where you learn the file name you need to ask for.
The last four digits are the UTC of the image, available every 10 min, i.e., 0000, 0010, 0320 etc. Himawari data are also excellent throughout the South Pacific.
This sample image is from 2 days later than other examples shown.
(4) Near live ASCAT winds
To get near live ASCAT winds, follow articles we have online about it and use links like the following for Central Japan waters:
You can use the same set of links for Northern Japan by changing the file number to 253, and for Southern Japan use 242. You can get these online or ask for them from Saildocs by email. For background see starpath.com/ASCAT.
Sample ASCAT pass
(5) Live ship reports You can also get a list of all ship reports near Japan by sending a blank email to shipreports@starpath.com and put the central Lat Lon in the subject line, such as 37.0 N, 140.2 E. (See starpath.com/shipreports.) This gets a list of all the reports plus a GPX file of the reports that can be loaded into a nav app to see actual locations and data.
(6) Ocean Currents. You can get ocean currents and SST for that region from RTOFS request to Saildocs
(7) Waves and sea state. GFS is best for this, again available from Saildocs. There are many sea state parameters (see Grib School list), but these are likely of interest most often:
Significant Wave Height of the Combined Seas (HTSGW)
To get the latest Japan waters text reports from Saildocs, use send Met.11por
To see how to get reports for other parts of the large metarea XI, use send metarea
Other metareas around the world...
(9) Special sources (with thanks to Mark D'Arcy for this reminder)
JMA, like other maritime nations, has weather models of their own, but the grib format is a paid service. You can see their MSM model at windy.com, but the higher-res LFM is paid only.
Many maritime nations also have universities or other agencies that run a localized version of the Weather Research & Forecasting Model (WRF). These high-res data can be very useful when available. Japan and South Korea have WRF data available from selected resources, such as the weather and nav app Expedition.
